1. Field of the Invention
This invention is related to the process of tapering an object, and more specifically, an elongated object.
2. Description of the Prior Art
There are many methods and apparatus useful for tapering objects. Fiber optics involves the transmission of light through transparent fibers of glass. These optical fibers can carry light over distances ranging from a few inches to more than 100 miles. Some individual fibers measure less than 0.001 inch in diameter.
Optical fibers have an extremely pure core of glass and are surrounded by a durable covering called cladding. Light from a laser, light-emitting diode, light bulb, or some other light-emitting device enters one end of the optical fiber. As the light travels through the core, it is typically kept inside it by the cladding. The cladding is designed in such a way that it bends inward light rays that strike its inside surface. At the other end of the fiber, the light is received by a photosensitive device.
There are two basic kinds of optical fibers--single-mode fibers and multi-mode fibers. Single-mode fibers are generally used for long-distance transmissions. They have extremely small cores (typically 8-9 microns in diameter), and they accept light only along the axis of the fibers. As a result, single-mode fibers require the use of special lasers as a light source, and they need to be precisely connected to the laser, to other fibers in the system, and to the photosensitive detector. Multi-mode fibers have cores larger than those of single-mode fibers (typically 50-60 microns in diameter), and they can use more types of light sources and cheaper connectors than can single-mode fibers, but they cannot be used over long distances.
These optical fibers have a number of uses. In an optical circuit application, lasers transmit coded messages by flashing on and off at extremely high speeds. The messages travel through optical waveguides longitudinally formed in photopolymeric sheets where they may be added, divided, switched and/or modulated in a manner analogous to the way electrical signals are processed in a printed circuit board. The termination point of the optical waveguides must be precisely connected by means of optical fibers to photosensitive interpreting devices that decode the messages and convert them back into the original form of the signal. Two significant advantages in using this optical circuitry to transmit data are the speed and lack of susceptibility to electrical noise.
However, a large problem in inexpensively achieving satisfactory optical circuits has been the troublesome interconnection between the waveguide within the photopolymeric web and the optical fiber. The center of the optical fiber must be precisely aligned, both axially and translationally, with the waveguide to minimize energy loss. In order to aid in this alignment, typically, the waveguide will stop just prior to reaching the edge of the web. There, a smaller diameter rectangular hole will be extended to reach the edge of the web. The longitudinal and translational axes of this hole are centered along those of the solid waveguide. The rectangular hole acts as a guide to precisely align the optical fiber with the center of the waveguide and to provide the fiber a snug fit into the circuit.
This arrangement while utilitarian is at once problematic. In order to effectively transfer light signals at the waveguide/optical fiber interface, the fiber must be cleaved transverse to its longitudinal axis such that its face is substantially flat. The process of cleaving the glass fiber leaves a sharp outer edge around the circumference of the cut. The diameter of the fiber is marginally larger (approximately 5 microns) than that of the rectangular hole so that the soft photopolymer walls must give slightly to accommodate the fiber's entry. As an operator attempts to insert the fiber into the end of the waveguide, often with the aid of a microscope, the sharp edges of the glass fiber slice away tiny shavings from the walls of the soft photopolymer. These shavings are pushed ahead of the fiber during the insertion process and block or otherwise interfere with the light path between the waveguide and optical fiber.
The prior art has dealt with various schemes to eliminate production of these troublesome shavings that disturb the light path at the waveguide/optical fiber interface. Most attempts have sought to taper the edges of the glass fiber around its circumference so that when it is threaded only a smooth bore encounters the soft photopolymer that makes up the waveguide walls. The primary problem with this approach is that the face of the optical fiber must remain flat for effective light transfer. The size of the glass fiber is small and it is indeed a challenge to taper or bevel its edges and leave the face of it intact.
U.S. Pat. No. 4,754,576 teaches a method of tapering using a translatable and rotatable microscope for viewing the tapering process and a fixed angled rotating pad to perform the taper. The problem with such a method is that it involves the time consuming process of setting a series of micrometers and an operator to be present to watch and limit the grinding operation. The fixed angle of the rotating polishing pad does not allow the operator to choose a specific angle of taper. And the manner of tapering is performed so that an additional heating step can take place to form a lens at the end of the fiber.
It is an object of the instant invention to provide a preferred solution to the general tapering problem for elongated objects.
It is also an object of this invention to provide a simple method of tapering an optical fiber, while leaving the active portion of its face flat for optimum light transfer.
It is an additional object of this invention to provide a method of adjusting the angle of taper of an optical fiber within a desirable range.
It is a further object of this invention to provide a fast method of achieving a desired taper to the optical fiber.
It is, moreover, an object of this invention to provide substantially uniform tapering around the circumference of the glass fiber.
It is a still further object of this invention to free the operator from the task of constantly monitoring the tapering operation to ensure a satisfactory result.